Mine Wastewater Treatment Technology
Background of mine wastewater research
The antimony mine in Lengshuijiang has a history of more than 120 years. It is the birthplace of the world’s antimony industry and the largest refining and processing place for antimony in the world. Due to the long time, large output and extensive methods of mining and smelting in the antimony industry, a large amount of heavy metals have been discharged into the environment in various forms for a long time. Among them, the slag leachate has caused serious heavy metal pollution in some water bodies in the tin mining area, and also caused soil pollution and pollution. Air pollution poses a threat to the health of surrounding residents and damages the quality and safety of planted crops. Heavy metal pollution has become the most prominent environmental problem in tin mining areas.
Main components and characteristics of mine wastewater
2.1 Main components of mine wastewater
Mine wastewater comes from mine natural leaching water, slag leachate, and wastewater discharged from mining sites, ore dressing plants, tailings dams, slag dumps, and living areas. The pollutants are mainly arsenic and antimony, and also contain lead and cadmium. , chromium, selenium, manganese and other heavy metal elements, and also contain certain oil substances, the proportion of which is closely related to the resources of the mine; and the mining and processing of the mine will not only produce waste water, but also lead to a large amount of movement. Plant death, which makes it possible for large amounts of organic and bacterial contaminants to be present in mine wastewater.
2.2 Main characteristics of mine wastewater
First, mine wastewater has a wide range of pollution and has a wide impact area.
The pollution caused by mine wastewater is not limited to the mining area, and the polluted area even extends to the entire watershed. For example, the problem of antimony pollution in tin mines. The areas subject to antimony pollution are not only tin mines, but also surrounding areas, and even the Zijiang River Basin where they are located has also suffered antimony pollution.
Second, the discharge of mine wastewater is large, multi-faceted and long-lasting. For example, tin mines have been polluted for a long time, and the amount of mine wastewater is very large, about 60,000 tons per day on average. In case of precipitation, the amount of wastewater is even greater.
Third, the composition of mine wastewater is complex and its concentration is extremely unstable. After long-term tracking, monitoring and analysis, the main excessive factors of mine wastewater in the tin mine area are arsenic and antimony.
Mine wastewater treatment technology
3.1 Preprocessing technology
In the production process of mine wastewater, there must be a large number of floating objects, large particles and even a large area of oil film. The existence of these substances will not only affect the effect of subsequent wastewater treatment technology but also cause blockage and damage to wastewater treatment facilities and equipment. Therefore, Mine wastewater must be pretreated first, and then the mine wastewater can be pretreated by means of filtration, flotation, radial flow, flocculation, etc. before subsequent treatment.
3.2 Acid-base neutralization technology
Mine wastewater usually fluctuates in pH value, and due to the existence of a large number of acidic pollutants, heavy metal pollutants, and organic pollutants, the proportion of mine wastewater is acidic, and the pH has a certain impact on the subsequent chemical and biological treatment technologies, usually Under the circumstance, acid-base neutralization treatment is required to keep the mine wastewater in a neutral state, so that the subsequent wastewater treatment effect is better.
Usually, acid mine wastewater can be neutralized with lime mixed with NaOH and CaOH, and alkaline mine wastewater can be treated with hydrochloric acid or sulfuric acid, but I do not recommend using mineral acid for alkaline wastewater treatment, because it will Sodium chloride or sulfate will be produced in wastewater, which cannot be accommodated by natural water bodies, and will also affect subsequent treatment equipment.
3.3 Heavy metal treatment
3.3.1 Vulcanization method
The sulfidation method is a treatment method in which the heavy metal ions in the wastewater are formed into insoluble substances by using vulcanizing agents such as Na2S, NaHS, and H2S, and then the heavy metal ions can be separated from the water through flocculation and filtration. Insoluble substances need further treatment to be released, so the author recommends using the sulfurization method to treat heavy metal ions that are difficult to handle.
The sulfidation method has the advantage of being different from other heavy metal treatment methods. After the heavy metal sulfide is formed, the pH value of the mine wastewater is between 7 and 9. The wastewater treated by the sulfidation method does not need to be neutralized, and can replace the acid-base neutralization treatment. link.
3.3.2 Heavy metal treatment agent
After the heavy metal treatment agent is used, the heavy metal ions can be formed into crystal grains, and the wastewater can be purified by flocculation or filtration. The use of heavy metal treatment agent can remove a variety of heavy metal ions in mine wastewater at one time, and this treatment agent is simple and convenient to operate, has strong adaptability to the water quality to be treated, and does not have too many restrictions. The crystal grains produced by heavy metal ions are easily dehydrated, which makes the subsequent treatment of this treatment method relatively easy.
3.3.3 Redox method
Redox is a wastewater treatment method that makes heavy metal ions easier to precipitate through redox reactions. For example, the iron powder redox method invented by a Japanese mining company uses the reducibility of iron to remove Cr(VI) from chromium-containing wastewater, and then precipitates heavy metal ions in the form of metals, which is not only conducive to the purification of wastewater, but also to the Heavy metal recovery effectively improves the economic benefits of wastewater treatment.
3.4 Treatment of organic pollutants
3.4.1 Constructed wetland treatment technology
Constructed wetland is a biological treatment technology. In the process of wastewater treatment, the interaction between substrates, aquatic plants and microorganisms is fully utilized, and the organic pollution in mine wastewater is realized through a series of functions such as filtration, precipitation, adsorption, and decomposition unique to wetlands. The high-efficiency degradation of substances enables the purification of mine wastewater.
Constructed wetlands have limited effect on heavy metal treatment, large area and low treatment efficiency. They are more suitable for the terminal treatment of large-scale mine wastewater, and are also more suitable for mine excavation and soil restoration and maintenance after damage. It belongs to sustainable mining. A major research direction for development.
3.4.2 Biofilm Technology
Biomembrane technology is a special semi-permeable membrane permeation purification technology. The organisms are attached to the biological turntable and other equipment to form a stable and semi-permeable biomembrane. Molecular motion pressure is the driving force, which makes the wastewater slowly flow through the biofilm, and the biofilm intercepts and separates the pollutants. It is a high-efficiency, energy-saving and simple-equipment wastewater purification technology. The problem with the application of biofilm technology is that the equipment is expensive, the maintenance and operation and maintenance costs are high, and the utilization rate is low; the work efficiency is greatly affected by the outside world, and it is not suitable for all mine wastewater treatment.
Mine wastewater is the most important pollution method in mining and processing. In order to ensure a virtuous circle between my country’s economic development and environmental protection, and avoid regional environmental pollution similar to the tin mining area in Lengshuijiang City.
In order not to make resources and the environment pay for development and to achieve sustainable development of resource industries, the author suggests that the government and enterprises where the mines are located should strengthen their investment in the treatment of wastewater generated during mining and processing.
Adopt more advanced, more efficient, more environmentally friendly and energy-saving equipment and processes.
According to the composition and properties of mine wastewater, the collocation of treatment technology and the setting of process flow should be carried out, the effect of mine wastewater treatment should be given the first place, the reuse of treated reclaimed water should be second, and the recovery of heavy metals should be the last, so as to maximize the improvement of mine wastewater. processing efficiency and contribute to the sustainable development of the mine.